Electric light



. Dec. 8,1925. 1,564,471

c. w. DAKE ELECTRIC LIGHT Original Filed Feb 23. 1923 Jitorngyg PatentedDec. 8, 1925.

UNITED STATES FATEN'E' @FFEQE.

CHARLES W. DARE, OF CHICAGO, ILLINOIS.

ELECTRIC LIGHT.

Original application filed February 23. 1923, Serial No. 620,581.Divided and this application filed.

February 29, 1924.

To all whom it may concern:

Be it known that 1, CHARLES TV. DAKE, a citizen of the United States,residing at Chicago, in the county of Cook and State of Illinois, haveinvented a certain new and useful Improvement in Electric Lights, ofwhich the fOllOWiIig' is a specification.

My invention relates to an improvement in electric lights for useespecially in connection with locomotive electric headlights and similarpurposes Where an incandescent electric light is used as the source foran illuminating or search light'ray associated with a parabolicreflector. This application is a division of my copending applicationSerial No. 620,561, filed February 23, 1923.

It is, of course, a known fact that the best place for such a source oflight is at the focal center of the reflector, and that the farther awaythe source gets from the focal center the less satisfactory becomes thelight.

It is impossible to have all of the light at the focal center, and Ihave discovered that the next best place is to have the light filamentstrung along the central axis of the reflector, passing through thefocal point. Next to this tlfe best place for the light is in a planeperpendicular to this axis and passing through the focal point.

Especially in connection with locomotive electric headlights where thevoltage is comparatively low, it is necessary, in order to get a lampwhich will comply with the necessary service conditions, to have afilament which is of comparatively great length, and in the past it hasbeen the practice to provide the filament arranged in a grid in a planeperpendicular to the focal axis.

I propose to provide in my bulb for incandescent light a comparativelylarge portion of the filament located on or immediately adjacent to andsurrounding this focal axis and projecting both in front of and behindthe focal point. I propose to locate the balance of the filament in theplane perpendicular to this axis and passing through the focal point.Experience shows that this arrangement results in a maximum ofillumination and prevents the presence of any dark spots or dark areasin the beam of light.

My invention is illustrated more or less diagrammatically in theaccompanying drawings wherein- Serial No, 895,893.

Figure 1 is a section through the reflector showing a side elevation ofthe light bulb in place therein;

Figure 2 is a perspective view of the bulb itself; and

Figure 3 is a top plan view thereof.

Like parts are illustrated by like characters throughout thespecification and drawings.

A is the glass bulb or globe of the conventional type of incandescentelectric light. It is provided with a screw-threaded base A adapted tobe screw-threaded into a socket and cemented as at A Projecting upwardlyfrom the base is a support A of glass or other suitable material, inwhich are imbedded or inclosed conductors A and A This supportterminates at its upper end in a base A from which project upwardly thethree supporting arms A, A A and a holding hook A Passing through thewall of the base A and associated with the conductor A is a conductorhook B, which is curved away from thefilament and terminates on thefocal line, where it supports the outward end of a coiled filament BThis coiled filament extends inwardly along the focal line, passingthrough the focal point, and is held by the hook A at a point behind thefocal plane. An inclined stretch or branch of this filament extends fromthe hook A to the support A", which terminates in the focal plane. Fromhere the filament extends to the hooks A A back to a point adjacent thehook A where it is carried by the conductor and support B which passesin through the wall of the member A and terminates at the conductor Athus giving an arrangement by which the coiled filament is supported incomparatively short coiled sections insulated except at the two endswhere it is mounted on the conductors, and anchored and positionedpartially in the focal line.

The filament itself is preferably formed of a single closely coiledspiral wire of the usual type. This coil is so fine and so close thatfor all practical purposes it may be treated and considered as a singlestraight wire, and while geometrically, of course, the size of thecoiled wire portion is large in fact, nevertheless, being placed righton the focal line as it is, it may for all practical purposes beconsidered as an incandescent filament on the focal line. The samecomment applies to that part of the filament located in a planeperpendicular to the focal line.

C is a parabolic reflector supported in any suitable manner. In the formherein shown the lamp base A penetrates the center of the reflector.lVhile this is the preferred form of my invention, 1 do not wish tolimit myself'to this use. I might mount the bulb with its base passingthrough the side wall of the reflector, the position of the filaments inrelation to the base being suitably changed to maintain the relation offilaments to the focal point or focal axis above described.

I claim:

1. The combination with a reflector havilig a focal axis and a focalpoint, of a single, ccntinuous luminous filament extending in part alongthe focal axis both in front of and behind the focal point and locatedin part in a plane perpendicular to the axis and intersecting it at thefocal point.

2. The combination with a reflector having a focal axis and a focalpoint, of a light bulb having a luminous filament comprising in part alongitudinal section lying along the focal axis of the reflector and aplurality of transverse sections at an angle to each other, located in aplane perpendicular to said axis at the focal point.

3. The combination with a reflector having a focal axis and a focalpoint, of a light bulb having a luminous filament comprising in part alongitudinal section lying along the focal axis of the reflector and aplurality of transverse sections at an angle to each other, located in aplane perpendicular to said axis at the focal point, the filament itselfcomprising a closely coiled wire spiral.

Signed at Chicago county of Cook and State of Illinois, this 26th day ofFebruary CHARLES W. DAK

